1. Field of the Invention
The present invention relates to liquid phase olefin polymerization, to the preparation of polyolefin products and to apparatus useful in the preparation of polyolefin products. In particular the present invention relates to apparatuses and equipment for the preparation of a variety of polyolefin products using a liquid phase polymerization process and to the methodology used in the operation of such apparatuses and equipment. More particularly, the present invention relates to apparatus and methodology which enhances the operation and control of polyolefin reactors.
2. Background of the Invention
Presently pending U.S. patent application Ser. No. 09/515,790 filed on Feb. 29, 2000 and entitled xe2x80x9cProcess For Producing High Vinylidene Polyisobutylenexe2x80x9d (hereinafter the ""790 application) relates to liquid phase polymerization processes for preparing low molecular weight, highly reactive polyisobutylene. In accordance with the disclosure of the ""790 application, a catalyst composition, which desirably may comprise a complex of BF3 and methanol, and a feedstock containing isobutylene, are each introduced into a reaction zone where the same are intimately admixed with residual reaction mixture so as to present an intimately intermixed reaction admixture in the reaction zone. The intimately intermixed reaction admixture is maintained in its intimately intermixed condition and at a relatively constant temperature of at least about 0xc2x0 C. while the same is in the reaction zone, whereby isobutylene therein is polymerized to form polyisobutylene (PIB) having a high degree of terminal unsaturation. A crude product stream comprising residual catalyst composition, unreacted isobutylene and polyisobutylene is then withdrawn from the reaction zone. The introduction of feedstock into and the withdrawal of product stream from the reaction zone are each controlled such that the residence time of the isobutylene undergoing polymerization in the reaction zone is no greater than about 4 minutes, whereby the product stream contains a highly reactive polyisobutylene product. Preferably, the reaction zone may be the tube side of a shell-and-tube exchanger in which a coolant is circulated on the shell side. A recirculation loop may desirably be employed to circulate the reaction admixture through the tube side reaction zone at a linear velocity sufficient to establish and maintain an intimately intermixed condition in the admixture and remove heat generated by the exothermic polymerization reaction.
U.S. Pat. No. 6,525,149 issued on Feb. 25, 2003 and entitled xe2x80x9cProcess For Preparing Polyolefin Productsxe2x80x9d (hereinafter the ""149 patent) relates to a novel liquid phase polymerization process for preparing a polyolefin product having preselected properties. The process of the ""149 patent includes the steps of providing a liquid feedstock which contains an olefinic component and a catalyst composition which may comprise a stable complex of BF3 and a complexing agent. The feedstock may comprise any one or more of a number of olefins, including branched olefins such as isobutylene, C3-C15 linear alpha olefins and C4-C15 reactive non-alpha olefins. The feedstock and the catalyst composition may desirably be introduced into a residual reaction mixture recirculating in a loop reactor reaction zone provided on the tube side of a shell and tube heat exchanger at a recirculation rate sufficient to cause intimate intermixing of the residual reaction mixture, the added feedstock and the catalyst composition. The heat of the polymerization reaction is removed from the recirculating intimately intermixed reaction admixture at a rate calculated to provide a substantially constant reaction temperature therein while the same is recirculating in the reaction zone. The conditions in the reactor are appropriate for causing olefinic components introduced in the feedstock to undergo polymerization to form the desired polyolefin product in the presence of the catalyst composition. A crude product stream containing the desired polyolefin product, unreacted olefins and residual catalyst composition is withdrawn from the reaction zone. The introduction of the feedstock into the reaction zone and the withdrawal of the product stream from the reaction zone are controlled such that the residence time of the olefinic components undergoing polymerization in the reaction zone is appropriate for production of the desired polyolefin product.
U.S. Patent publication 2003-0040587 A1 published on Feb. 27, 2003 and entitled xe2x80x9cMid-Range Vinylidene Content Polyisobutylene Polymer Product And Process For Producing The Samexe2x80x9d (hereinafter the ""587 publication) describes a mid-range vinylidene content PIB polymer product and a process for making the same. In accordance with the disclosure of the ""587 publication, at least about 90% of the PIB molecules present in the product comprise alpha or beta position isomers. The alpha (vinylidene) isomer content of the product may range from 20% to 70% thereof, and the content of tetra-substituted internal double bonds is very low, preferably less than about 5% and ideally less than about 1-2%. The mid-range vinylidene content PIB polymer products are desirably prepared by a liquid phase polymerization process conducted in a loop reactor similar to the reactors described in the ""790 application and the ""587 patent at a temperature which desirably may be about 60xc2x0 F. or higher using a BF3/methanol catalyst complex and a contact time of no more than about 4 minutes.
The ""790 application, the ""587 publication and the ""149 patent are each assigned to the assignee of the present application, and the entireties of the respective disclosures thereof are specifically incorporated herein by this reference thereto.
In conducting the reactions described above, highly specialized equipment may often be employed to enhance the operation and control of the polymerization reactors. In each case, for example, the crude product leaving the reactor may be contaminated with residual catalyst which desirably should be quickly quenched or killed to avoid further polymerization of monomers and low molecular weight oligomers without appropriate cooling and/or isomerization resulting from shifting of the position of the remaining double bond. The catalyst composition may be subjected to contamination by residual materials recirculating with the reaction admixture during the conduct of the polymerization reaction. Moreover, as in any industrial activity, methodology and/or equipment for enhancing capacity and throughput are sought continually.
It is an important aim of the present invention to satisfy the needs discussed above. In this regard, in one very important aspect of the invention, the same provides apparatus for olefin polymerization which includes a plurality of reactors. In accordance with the concepts and principles of the invention, each of these reactors desirably may comprise structure defining a reaction zone, an olefin polymerization reaction mixture inlet connection and a olefin polymerization reaction mixture outlet connection. These connections desirably are in fluid communication with the reaction zone. The reactors are each adapted and arranged to facilitate the conduct of an exothermic olefin polymerization reaction in the reaction zone.
In further accordance with the concepts and principles of the invention, each of the reactors also may include a recirculation system including a pump arranged and adapted to circulate the reaction mixture in the reaction zone independently of the introduction of olefin containing feedstock into the reactor.
The apparatus of the invention also desirably includes an olefin containing feedstock distribution assembly that comprises an olefin containing feedstock inlet and a plurality of olefin containing feedstock outlets. The arrangement of the distribution assembly being such that each of the feedstock outlets is connected in fluid communication with the reaction zone of a respective reactor. The apparatus of the invention may also desirably include a product collection assembly including a plurality of crude polyolefin product inlets and a crude polyolefin product outlet, the arrangement of the collection assembly being such that each of the crude polyolefin product inlets is connected in fluid communication with the reaction zone of a respective reactor.
Broadly, the apparatus of the invention may include two or more of the reactors, for example three or four or five or six or more of the reactors.
In another important aspect of the invention, the same provides a method for olefin polymerization. In accordance with the invention, the method includes providing a plurality of reactors, each of which defines an internal reaction zone. The method also includes supplying an olefin containing feedstock, dividing such feedstock into a plurality (2, 3, 4, 5, 6 or more) of separate feedstock streams, introducing each of the feedstock streams into a reaction mixture circulating in the reaction zone of a respective one of the reactors, and conducting an exothermic olefin polymerization reaction in each of the reaction zones.
The method of this aspect of the invention also includes the steps of separately circulating the reaction mixture in each reactor independently of the introduction of the respective stream of feedstock into the reaction mixture, removing a respective crude polyolefin product stream from the reaction mixture circulating in each of the reactors, and combining the crude polyolefin product streams to form a single crude product stream.
In another aspect, the invention provides a reactor apparatus for olefin polymerization which comprises at least one reactor defining a reaction zone and including an olefin polymerization reaction mixture inlet connection and an olefin polymerization reaction mixture outlet connection. These connections may desirably be in fluid communication with the reaction zone. The reactor is adapted and arranged to facilitate the conduct in the reaction zone of an exothermic olefin polymerization reaction on the reaction mixture in the presence of a catalyst composition comprising a catalyst and a catalyst modifier. In accordance with this aspect of the invention, the reactor apparatus further includes a feedstock inlet, a crude product outlet and a recirculation system including a pump arranged and adapted to circulate the reaction mixture in the zone independently of the introduction of feedstock into the reaction mixture via said feedstock inlet. The reactor apparatus of this aspect also includes a catalyst composition inlet in fluid communication with the zone facilitating the addition of catalyst composition to the olefin polymerization reaction mixture and at least one catalyst modifier inlet in fluid communication with the zone facilitating the addition of catalyst modifier to the olefin polymerization reaction mixture at a rate that is independent of the rate of addition of the catalyst composition.
Another important feature of the invention includes the provision of a method for operating an olefin polymerization reactor. This method includes the steps of providing an olefin polymerization reactor having a reaction zone, recirculating an olefin polymerization reaction mixture in the zone, introducing an olefin containing feedstock into said reaction mixture, said polymerization reaction mixture being recirculated at a flow rate which is independent of the rate of introduction of the feedstock into the recirculating olefin polymerization reaction mixture, introducing a catalyst composition comprising a catalyst and a catalyst modifier into the recirculating olefin polymerization reaction mixture, subjecting the polymerization reaction mixture to exothermic olefin polymerization reaction conditions in the zone in the presence of the catalyst composition, and introducing a catalyst modifier into the recirculating olefin polymerization reaction mixture at a rate that is independent of the rate of introduction of the catalyst composition.
In accordance with the concepts and principles of the invention, the foregoing system and methodology may be used in connection with a system and/or methodology which includes only a single reactor vessel or with one which includes a plurality of reactor vessels arranged in parallel as described above. In this regard, it is to be noted that in accordance with the invention, the invention further provides an apparatus and/or a method which includes a multi-reactor system as described above in combination with the described system for introducing catalyst modifier into the recirculating reaction mixture at a rate that is independent of the rate of introduction of the catalyst composition.
It is an additional aspect of the invention to provide a crude polyolefin product catalyst removal and wash system. In accordance with this aspect of the invention, the catalyst removal and wash system comprises an upstream settler vessel defining an internal settlement chamber adapted and arranged for receiving a mixture of a crude polyolefin product and an aqueous wash media and allowing the product and the media to separate therein under the influence of gravity. The system further includes a crude, catalyst containing olefin polymerization product inlet line in fluid communication with the chamber of the upstream settler vessel, a catalyst killing agent inlet conduit in fluid communication with the chamber of the upstream settler vessel, and a first make-up water inlet passageway in fluid communication with the chamber of the upstream settler vessel.
In addition to the foregoing, the catalyst removal and wash system desirably includes a downstream settler system including at least one downstream settler vessel defining an internal settlement chamber adapted and arranged for receiving a mixture of a partially washed crude polyolefin product and an aqueous wash media and allowing the product and the media to separate therein under the influence of gravity, an overhead, partially washed polyolefin product line intercommunicating the chamber of the upstream settler vessel with the downstream settler system, a washed crude olefin polymerization product outlet line in fluid communication with the downstream settler system and a second make-up water inlet passageway in fluid communication with the downstream settler system. Finally, the system includes a first drain line intercommunicating the chamber of the upstream settler vessel with an inlet connection to a waste water receiving system, and a second drain line intercommunicating the downstream settler system with the inlet connection to the waste water receiving system. Thus, used wash water from the upstream and downstream portions of the system may be purged separately from the system.
In accordance with the foregoing aspect of the invention, the downstream settler system may include one or two or three or more separate settler vessels
Yet another important feature of the invention is the provision of a method for treating a catalytically formed crude polyolefin product containing residual catalyst to avoid further reaction in the product and remove residual catalyst therefrom. In accordance with this aspect of the invention, the method comprises intimately admixing crude residual catalyst containing polyolefin product and a first aqueous media containing a catalyst killing agent to thereby form a first intimately admixed two phase, gravity separable mixture, introducing the first two phase mixture into a first settlement zone and allowing the same to settle in the first zone under the influence of gravity to present an upper partially washed crude polyolefin product phase and a first lower aqueous phase containing dissolved catalyst salts, withdrawing the first lower aqueous phase from the first settlement zone and recirculating a first portion thereof and introducing the same into the first two phase mixture for inclusion as part of the first aqueous media, directing a second portion of the first lower aqueous phase to a drain for disposal or reclamation, introducing a first quantity of make-up water into the first two phase mixture for inclusion as part of the first aqueous media, withdrawing the partially washed crude polyolefin product phase from the first settlement zone and intimately admixing the same with a second aqueous media to thereby form a second intimately admixed two phase, gravity separable mixture, introducing the second two phase admixture into a second settlement zone and allowing the same to settle in the second zone under the influence of gravity to present an upper more fully washed crude polyolefin product phase and a second lower aqueous phase, withdrawing the second lower aqueous phase from the second settlement zone and recirculating a first portion thereof and introducing the same into the second two phase mixture for inclusion as part of the second aqueous media, directing a second portion of the second lower aqueous phase to a drain for disposal or reclamation, removing the more fully washed crude polyolefin product phase from the second settlement zone, and introducing a second separate quantity of make-up water into the second two phase mixture for inclusion as part of the second aqueous media.
It is to be noted that the catalyst removal and wash system and/or method described above is suitable for use in connection with either a system which includes only a single reactor as well as one which includes a plurality of reactors as described above. Thus, it is an important aspect of the invention to provide a system and/or method which includes both a multi reactor system and a catalyst removal and wash system and/or method as described. In addition, such combined system may also include the described system for adjusting the amount of catalyst modifier in the recirculating reaction mixture.